Heart rate variability and heart rate turbulence in patients with vasovagal syncope.

Aim    The autonomic nervous system plays an important role in the pathogenesis of vasovagal syncope, but studies on the effect of basal autonomic tone have found confusing results. The aim of this study was to investigate the effect of basal autonomic functions, as assessed by heart rate variability (HRV) and heart rate turbulence (HRT), in patients with vasovagal syncope.Material and methods    Patients who underwent head-up tilt test (HUTT) due to unexplained syncope and who had a 24 hr Holter ECG recording in the same period were retrospectively analyzed. Patients with diabetes, a history of myocardial infarction, heart failure, orthostatic hypotension, atrial fibrillation, or use of vasoactive drugs, such as beta blockers, were excluded from the study. 161 patients who met these criteria were included in the study. Time domain HRV parameters from Holter ECG recordings and HRT parameters from patients with sufficient number of ventricular premature contractions were measured.Results    The age of the patients varied from 16 to 75 yrs (mean: 44.8±18.5 yrs). HUTT results of 60 (37.2 %) patients were evaluated as positive. There were no significant differences in the basal demographic, clinical, or laboratory findings of the tilt-positive and tilt-negative patient groups. Likewise, there were no significant differences between the time domain HRV parameters and HRT parameters of both groups.Conclusion    HRV and HRT parameters reflecting basal autonomic function were not different between HUTT positive and HUTT negative patient groups. These findings suggest that basal autonomic functions have no effect on vasovagal syncope pathogenesis.